What Measures Are Required Prior to Spray Foam Applications?

In this article, we discover some of the measures we take at Spray Foam Tech to assess and manage the moisture in the builds prior to spray foam insulation applications. This includes running static & dynamic condensation risk analysis (hygrothermal condensation risk assessment).
What Measures Are Required Prior to Spray Foam Applications?

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Heat and Moisture Transport

Heat and moisture transport are intrinsically coupled physical phenomena. Hygrothermal building physics describes these coupled transport processes. Because of this coupling, retrofitting building fabric to improve its thermal performance is likely to also impact its moisture performance, particularly in traditional construction.
Therefore to avoid moisture-related deterioration of the building fabric and health risks, retrofit measures need to be assessed not only for their thermal benefits but for their hygrothermal impacts too.
Current governmental policies in the United Kingdom (UK) aim at significantly reducing greenhouse gas emissions, a large portion of which is associated with emissions from buildings in the form of carbon dioxide (CO2). 
In the UK, space heating accounts for 65% of residential energy use. The focus on the thermal performance of the building envelope, therefore, has increased greatly over the last decades, with building regulations requiring an ever better thermal resistance of roofs, external walls, windows etc, in order to reduce the required cooling and heating demand and, in turn, associated CO2 emissions and fuel costs.
Heat transfer, however, is intrinsically coupled with moisture transport. The hygrothermal performance of building elements is the coupled heat and moisture transport that occurs within and through them, as influenced by their material characteristics and external conditions.
The deterioration and decay that occurs in buildings almost always involve water. Moisture accumulation and transport within the building fabric can lead, for example, to structural damage, spalling due to freeze-thaw, decay through rot, salt efflorescence and reduced thermal performance of insulants.
Moisture accumulation can also result in mould growth, a health risk for building occupants. Due to the coupled nature of heat and moisture transport, changing the thermal performance of the building envelope is likely to also change its moisture performance. 


The mass of a material is often discussed using bulk density (ρ), a material property which describes the mass of a material per unit of volume. Density is normally given in units of grams per cubic centimetre [g/cm3] or kilograms per cubic metre [kg/m3], where 1 g/cm3 = 1000 kg/m3.
An important distinction must be made between the term particle density, describing the microscopic, molecular property of any particular substance, and bulk density, which is a macroscopic property that depends on physical geometry.
For example, a solid steel block and an equivalent mass of steel wool are made of the same material and have the same particle density. However, because of the physical configuration of steel wool, which includes a large number of airspaces between the fibres, the volume of a steel wool sample will be much larger and the steel wool will therefore have a much lower bulk density.
Whereas particle density is an intrinsic material property that does not change in common practice, bulk density will change with configuration.  For example, our closed cell foam high density shows 35 kg/m3.

Permeability / Vapour resistance

Whereas porosity is concerned with the quantity of pores in a material, permeability describes the connectivity of pores with each other and the environment surrounding the material. Parts of a pore structure are open to a material’s surface, or boundary, connecting the pore structure to an adjacent material or the greater environment.
Thereby, air and moisture from the environment can enter and leave a material via the pore structure. However, it does not automatically follow that all pores in a material are connected to each other.
In fact, some pore connections may be dead ends; others may be small pore structures isolated from the rest, i.e. ‘ink bottle’ or ‘blind’ pores. Some pore structures will be connected to the surfaces of the materials and linked in a continuous path. 
Pore structures with a large proportion of interconnected networks, are called open-pore structures; whereas pore structures with mostly isolated pores or isolated pore networks are referred to as closed-pore structures.
In an open-pore structure, “a nanoscopic ant could wander throughout the void space and eventually visit all points within it. This means that all pore space is available for flow of gas or liquid and is in communication with the environment in which the material finds itself.
Moisture transport by vapour convection may be reduced by good workmanship and increased attention to airtightness, but it cannot be eliminated completely in practice. Therefore, condensation due to vapour convection must be allowed to dry out to avoid accumulation.
In this regard, vapour barriers can sometimes do more harm than good, because they prevent vapour from evaporating to the room by diffusion when outside surface temperatures are higher than the room’s ambient temperature.
This is common in summer (thus is often called summer diffusion) but it can happen due to thermal radiation on sunny days at any time of the year. For example, our open cell foam shows 0.700 (h.m2.Pa)/mg.

Thermal Conductivity (K Value / Lambda Value)

Thermal conductivity also referred to as the K value and Lambda value is the rate at which heat is transmitted through a material, measured in watts per square metre of surface area for a temperature gradient of one Kelvin per metre thickness (W/mK). The lower the K value, the better the thermal efficiency of the material.
Lambda Value
Open cell foam
Closed cell foam 

Thermal Resistance (R Value)

Thermal resistance, or R value, is measured in W/m2K and is equal to the thickness divided by the conductivity. The resistances of each material are added together to determine the overall resistance of the construction. The higher the R value, the more efficient the insulation Closed Cell foam  = 0.1 ÷ 0.020 = 5.0W/m2K 100mm Open cell foam = 100mm ÷ 0.040 = 2.5W/m2K
Surfaces also provide thermal resistance and there are standard figures for these resistances that must be taken into account when calculating U-values:
Internal Surface Resistance = 0.13W/m2K
External Surface Resistance = 0.04W/m2K

Thermal Transmittance (U value)

Thermal transmittance, or U value, is a measure of the rate of heat loss of a roof or wall construction. It is expressed as watts per square metre, per degree Kelvin (W/m2K).
The U value is calculated from the reciprocal of the combined thermal resistances of the materials in the element, air spaces and surfaces. Effects of support bars and brackets causing thermal bridges, and fixing screws should also be taken into account.
Thermal transmittance differs from thermal conduction, in that thermal transmittance is actually a combination of thermal conductions, thermal convection and thermal radiation through the material. However, radiative or convective properties of material surfaces are not accounted for.
Although thermal conductance is the dominant heat transfer mechanism in solid materials, in loose and porous materials thermal convection and radiation also contribute to their thermal transmittance. 

Thermodynamic temperature

Is the measure of the average energy of all of the vibrational, rotational and translational motions of these particles. It is not surprising then that, unlike temperature, thermodynamic temperature is always measured from absolute zero.
thermodynamic temperature
The full variety of these motions constitutes the internal energy of the body (commonly known as its thermal energy). Kilowatt-hour is used to describe the amount of energy transferred over a certain period of time. 1 kWh = 3.6 MJ (megajoule).
The energy use of a building’s space heating system is, for example, normally stated in kilowatt-hours. The energy transferred in large generating plants or whole economies might be described in GWh or TWh.
Finally, kWh/(m2∙yr) describes the amount of energy transferred over a year per square metre of the thermal envelope: the key unit of measure for building energy rating. 
As a body is heated or cooled its internal (or thermal) energy will change and thus its temperature. The thermal inertia of a body is given by its specific heat capacity (cp), the amount of heat required to change one kilogram of the material by one degree and is given in units of joules per kilogram and per kelvin [J/(kg∙K)].
Bodies with high specific heat capacity require more energy to raise their temperature by one degree. 

Thermal Conduction

Thermal conduction is a direct heat transfer mechanism from molecule to molecule caused by collisions between the molecules. If two bodies are touching the one with stronger molecular movement will be termed the one with greater temperature.
Transferring its internal energy, i.e. heating, will increase the agitation of the second body’s molecules by chain reaction. Importantly thermal convection cannot occur in a solid and thermal radiation can only occur in a non-opaque solid such as Germanium (which is why this metal is used in the lens of thermographic cameras).
However, thermal conduction can occur in fluids, i.e. liquids and gases, because collisions of molecules can occur. 
The measure of how quickly thermal energy is transferred by conduction through a material is thermal conductivity (λ) (previously termed k-value), given in units of watts per metre and per kelvin of temperature difference [W/(m∙K)].
Conductivity is dictated by a material’s molecular and pore structure and is independent of the material’s shape or dimensions. The term thermal conductance describes the conductivity of a material that is dependent on its shape and dimensions and is therefore given in units of watts per square metre per kelvin of temperature difference [W/(m2∙K)].
Thermal conductance should not be confused with thermal transmittance, or U-value, which is a combination of thermal conduction, thermal convection (where air cavities are present) and radiation. 
Compared to liquids and solids, gases are less conductive. Many insulation materials rely on this fact by having a closed pore structure which entraps less conductive air or other gases within the material.
Air is a good insulant, particularly when relatively dry, but some other gases have better insulating properties. Gas layers are therefore commonly used in building construction to improve heat retention, and the entrapping of small pockets of gas within the closed pore structure of non-woven quilt or foam materials is the key principle behind a large number of present-day insulants. 

Thermal convection

Thermal convection is a heat transfer mechanism whereby a fluid is brought into motion, either by gravity or another force, transferring thermal energy from one molecule to another and thus from one place to another.
Strictly speaking, thermal convection is a combination of thermal conduction and thermal advection.The latter is solely heat transfer by bulk fluid flow. Where a fluid meets a solid surface heat is transferred conductively. 
An example of thermal convection in water is the circulation of hot water inside the pipes of a non-pumped, water-based heating system. 

Vapour convection

Water vapour is a component of air, movement of air will always entail vapour transport. This transport mechanism is called vapour convection. It relies on bulk fluid flow, in this case the movement of a body of air. Without air movement to transport the moisture, vapour convection cannot occur.
In other words: still, air, i.e. still-standing or immobile air, cannot transport moisture by convection. (Air can also transport small quantities of liquid moisture in the form of droplets, such as steam when cooking.
So strictly speaking, the term moisture convection should be used to include both transport of gaseous and liquid moisture. As vapour convection is moisture transport by airflow, it requires an understanding of air movement. To control convective moisture transport independently from indoor and outdoor pressure and temperature differences forced convection is often used. This normally comes in the form of mechanical fan ventilation systems, by which the fan forces airflow in one direction.
Mechanical ventilation can be an efficient method of removing larger quantities of moisture quickly from a room to the outdoors and is therefore often used in rooms where larger quantities of moisture are often produced, such as bathrooms, kitchens and utility rooms. 

Vapour diffusion

Vapour diffusion is the movement of molecules due to differences in concentration, driving particles from areas of high concentration to areas of lower concentration. Diffusion differs from convection in that diffusion does not require a current.
Vapour pressure is the driving force for vapour diffusion. Reversely, it will always act to distribute vapour molecules to equalise vapour pressure. Vapour diffusion and vapour pressure are inextricably linked. However, temperature also plays an important role, as vapour diffusion is driven by the gradient of vapour pressure, diffusion always goes from regions with high vapour pressure towards regions with low vapour pressure.
Diffusion occurs through still air and, more slowly, through the pores of porous materials. The rate of diffusion through a material is affected by the properties of that material, which are particularly dependent on the form of its pore structure.
How difficult it is for vapour to move through a material, compared to still air, is described with the unit-less water vapour diffusion resistance factor (μ-value), sometimes also referred to as vapour resistance factor or diffusion resistance factor. This value reflects the combined impacts of pore size, pore connectivity and tortuosity.
There is an abundance of terminology used to describe the ability of vapour to move through porous materials. Like the μ-value, vapour resistivity, measured in units of mega-newton seconds per gram and per metre [(MN∙s)/(g∙m)].


In buildings with low levels of airtightness and with little or no designed ventilation, air infiltration comprises an important, albeit haphazard and uncontrollable portion of the air supplied to the building occupants, but also leads to increased heat loss and lack of comfort.
Large rooms with high ceilings (a feature of many, but by no means all, traditional buildings) provide a greater volume to contain water vapour and other gases which can result in better indoor air quality than a similar room with equal air infiltration but a smaller volume. 
In buildings with high levels of airtightness (i.e. Q50 value < 5.0 m3/m2.hr) the required air exchange rates must be achieved by other means than occasional window opening and air leakage, e.g. through suitably designed, commissioned and maintained ventilation systems.
Once again this requirement is of greater importance in smaller rooms, and above all small bedrooms (where CO2 can be released for many hours without occupants modifying conditions by opening windows or internal doors).
There is mounting evidence that the greater the level of airtightness achieved the less suitable natural ventilation becomes as the means by which to deliver acceptable air quality, The best ventilation systems should provide good air quality at all levels of airtightness without undue heat loss, through modulated supply and extract of air or the use of heat recovery in ventilation systems.
When specified and installed well there needs to be little visual change and no loss in heritage value. The general aims of reducing air leakage and increasing airtightness raise a host of questions for traditional buildings: How will internal levels of relative humidity change, could there be an impact on interior decoration and objects? What will the new levels mean for the risk of mould growth? How will vitiated air be replaced with the fresh air needed by building occupants?
It is clear that reduced air leakage and increased airtightness impose a greater requirement for well-designed and well-functioning ventilation, particularly in locations where high vapour loads are produced, e.g. bathrooms, kitchens, and utility rooms. Yet, insulating retrofit work is all too often installed without even giving the slightest thought to the resulting ventilation requirements. 

Surface Condensation

surface condensation

Surface condensation occurs when moisture in the air comes into contact with a surface that is colder than the dew point temperature of the air. This can lead to moisture accumulating on the surface, which can in turn lead to mould growth, corrosion, and other problems.

To prevent surface condensation from occurring, it is important to properly insulate surfaces and maintain a consistent indoor temperature. Spray foam insulation is an effective way to prevent surface condensation by creating a barrier between the cold surface and the warm, moist air.

At Spray Foam Tech, we use high-quality spray foam insulation to ensure that your property is protected from surface condensation. Surface condensation as well occurs when water vapour in the air comes in contact with a cold surface, such as a window or uninsulated wall. This can lead to the formation of water droplets on the surface, which can then lead to mould growth and other issues. To prevent surface condensation, it’s important to ensure that your building is properly insulated and that there are no cold spots where moisture can accumulate. 

We prioritise the safety and satisfaction of our clients. This is why we utilise BuildDesk and WUFI software to ensure that our products are applied in a way that minimises the risk of condensation. By assessing the potential for condensation year-round, we can take preventative measures to avoid any issues that may arise.

Our accredited installers are highly trained and experienced, ensuring that our products are applied in accordance with the certification and parameters outlined in our calculations. By following these strict guidelines, we can guarantee that there is no risk of condensation when using our products and services.

We understand the importance of providing reliable and effective solutions to our clients, which is why we prioritise the use of advanced software and highly skilled installers. With Spray Foam Tech, you can have confidence in the quality of our products and the expertise of our team.

Interstitial Condensation

Interstitial Condensation

Interstitial condensation occurs when moisture in the air becomes trapped within the layers of a building’s structure. This can occur when warm, moist air from inside a building comes into contact with a cold surface, causing the moisture to condense and become trapped. Interstitial condensation can lead to rot, decay, and other structural damage. To prevent interstitial condensation, it is important to properly ventilate the building and use effective insulation. 

Spray foam insulation is an effective way to prevent interstitial condensation by creating a barrier between the warm, moist air and the cold surface. At Spray Foam Tech, we use high-quality spray foam insulation to ensure that your building is protected from interstitial condensation.

Interstitial condensation, as well, occurs within the building’s insulation. This can happen when warm, moist air from inside the building permeates through the insulation and comes into contact with a cold surface, such as the outer layer of the insulation or the exterior wall. This can lead to moisture buildup within the insulation, which can then lead to mould growth and other issues. To prevent interstitial condensation, it’s important to use insulation materials that have a high resistance to moisture penetration.

One key factor to consider when addressing both surface and interstitial condensation is partial pressure. Partial pressure is the pressure exerted by a single gas in a mixture of gases, such as the air inside and outside of a building. External and internal partial pressures are affected by factors such as temperature, humidity, and air flow. It’s important to understand how these factors can impact partial pressure and moisture buildup within your building’s insulation.

In order to properly address moisture buildup and prevent issues such as mould and mildew, it’s essential to work with a professional insulation contractor who has experience in identifying and addressing these issues. A professional contractor can assess your building’s insulation needs and recommend the best materials and techniques to ensure that your building remains dry and free from moisture-related issues.

At Spray Foam Tech, we specialise in providing high-quality insulation services that are designed to prevent moisture buildup and other common insulation-related issues. Our team of experienced professionals can assess your building’s insulation needs and recommend the best solutions to help you maintain a healthy, dry, and comfortable indoor environment. Contact us today to learn more about our insulation services and how we can help you protect your investment.

Partial Pressure

Partial pressure is a measure of the pressure that a gas exerts within a mixture of gases. In the context of building insulation, partial pressure is important because it can affect the movement of moisture through the insulation material. External and internal partial pressure can be affected by external temperature, humidity levels, and other factors. 

At Spray Foam Tech, we use BS EN ISO standards to measure external and internal partial pressure and ensure that our insulation products are effective at preventing moisture buildup and other problems.

External Temperature & Internal Temperature

External and Internal temperature is an important factor to consider when installing building insulation. External temperature can affect the rate at which heat is transferred through the insulation material, which can in turn affect the temperature and humidity levels inside the building. 

We use BS EN ISO standards to measure external & Internal temperature and ensure that our insulation products are effective at maintaining a comfortable indoor environment.

Overall, we are committed to providing high-quality insulation solutions that protect your property from surface and interstitial condensation, and other moisture-related problems. Our products are designed to meet BS EN ISO standards for measuring partial pressure and external temperature, ensuring that your property is properly insulated and protected from the elements. 

Dew Point

Dew point is a crucial parameter used to measure the moisture content in the air. It is the temperature at which the air becomes saturated with water vapour and starts to condense into liquid. Knowing the dew point is essential in various applications to prevent moisture-related problems and ensure optimal air quality.

At Spray Foam Tech, we understand the importance of monitoring the dew point, which is why we use the latest technology to measure it accurately. We use Buildesk, a software designed specifically for the UK, to measure the dew point temperature. This enables us to maintain the appropriate moisture levels and ensure that our work is of the highest quality.

The importance of monitoring the dew point lies in its ability to prevent moisture-related problems. High levels of moisture in the air can lead to mould growth, corrosion, and condensation, causing damage to buildings, equipment, and products. By monitoring the dew point, one can maintain the appropriate moisture levels and prevent such problems.

In industrial settings, measuring the dew point is crucial in compressed air systems. Compressed air must be kept dry to prevent damage to the equipment and ensure its efficient operation. The dew point of the compressed air must be maintained below a certain level depending on the type of equipment and application.

In construction and building maintenance, the dew point is essential in preventing structural damage and maintaining a healthy environment. Moisture in walls, ceilings, and floors can lead to mould growth, weakening of the structure, and health issues. By measuring the dew point of these surfaces, one can ensure that they are not too moist and prevent these problems.

In HVAC systems, the dew point is used to determine the optimal humidity levels for comfort and energy efficiency. By maintaining the appropriate dew point levels, one can ensure that the air quality is optimal and prevent health issues such as dry skin, allergies, and respiratory problems.

Understanding the dew point is essential in various applications to prevent moisture-related problems and ensure optimal air quality. Measuring the dew point using Buildesk software, as we do at Spray Foam Tech, is crucial in maintaining the appropriate moisture levels in industrial, construction, and HVAC systems. By monitoring the dew point, one can ensure a healthy and safe environment while preventing damage to buildings, equipment, and products.


In conclusion, prior to any spray foam application, it is essential to take the necessary measures to ensure a successful and safe installation. Following these guidelines will not only lead to a better spray foam application but will also ensure the safety of both the installers and the building occupants.

It is crucial to remember that spray foam insulation can be an excellent investment for any building, but only when installed correctly with proper precautions taken. By working with experienced and knowledgeable professionals, you can be confident in the quality and effectiveness of your spray foam insulation application.
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